When to Plant Onion in Alpine County, CA
Onions are a fundamental kitchen staple available in yellow, white, and red varieties. Choose long-day, short-day, or intermediate types based on your latitude.
Alpine County, California is in USDA Zone 5a. The average last spring frost is May 19 and the first fall frost is October 3, giving you a growing season of approximately 137 days.
At an elevation of 1,278 feet, Alpine County receives approximately 36.3 inches of rainfall annually with predominantly loam soil. Summer highs average 84°F, so choose short-season varieties of Onion to ensure they mature before fall.
Alpine County Soil Profile
Soil Type
Loam
Soil pH
6.4-7.3
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Onion Planting Timeline — Alpine County, CA
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 14 | Apr 14 – Apr 28 |
| Transplant Outdoors | May 19 | May 19 – Jun 2 |
| Direct Sow | May 5 | May 5 – May 26 |
| Fall Sowing | July 25 | Jul 25 – Aug 8 |
| Harvest | August 18 | Aug 18 – Oct 6 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors |
| July | Fall Sowing |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Moderate — regular watering
Days to Maturity
90–120 days
Soil pH
6 – 7
USDA Zone
Zone 5a
Growing Season
137 days
Growing Tips for Alpine County
Start seeds indoors 8-10 weeks before transplanting. Match day-length type to your latitude. Stop watering when tops begin to fall over and cure bulbs for 2-3 weeks before storage.
Companion Planting
Good Companions
Avoid Planting Near
Level Up Your Garden
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Alpine County, CA?
Alpine County is in Zone 5a with an average last frost of May 19. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Alpine County, CA?
Alpine County, California is in USDA Hardiness Zone 5a. The average last spring frost is May 19 and first fall frost is October 3.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Alpine County gardeners in Zone 5a organize planting dates, track what's growing, and never miss a planting window.
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